Project 1: Interference patterns
Consider two slightly separated transparent surfaces. When light hits on these surfaces, part of the light will reflect from both the surfaces. The interference will occur according to the distance between the surfaces. Constructive and destructive interference will occur, if the distance between the surfaces is a multiple of half or whole wavelengths of the light. This will produce an interference pattern.
What you need?
1.Two sheets of Plexi glass, or 1/8 inch (.64 or .33 cm) thick and approximately 1 foot (30cm) square. (size is not critical)
2.A piece of dark construction paper.
3.One 3x5 inch (8x13 cm) piece of transparent red plastic.
4.Electrical or duct tape.
5.A light source, such as desk lamp.
What to do?
1.Peel the paper from the plexi glass. If necessary, smooth all the edges using sandpaper. Be careful not to scratch the surfaces. By using alcohol and a soft cloth, you can clean the top and the bottom surfaces. To hold the plates in place, press the plates tightly together and tape around the edges. To make the interference patterns more visible, tape a sheet of dark construction paper to one plate.
2.Hold the plates with the dark paper side on the bottom, in any strong source of white light. You can see the rainbow coloured interference patterns and by bending, twisting or pressing on the plates, the patterns will change. You can also notice that the interference patterns strongly resemble the contour lines on a topographic map.
3.In between the light source and the plates, place the red plastic. Now you can notice that the patterns become red and black.
A thin air gap will separate the light waves reflected from the surfaces of the two plastic sheets.
After reflecting from the two surfaces, these light waves will meet. When these two waves meet, they can add together, cancel each other or partially cancel each other. The adding and cancelling of light waves is called constructive and destructive interference. This will create the rainbow coloured patterns that you see.
Project 2: Hole in the hand
You can make a hole appear on your hand by tricking your brain. Let us see how it is.
What you need?
Roll a piece of paper into pipe. Look through the tube with one eye after holding the tube with one hand next to the palm of your other hand. With the other eye look straight at your palm.
After a few seconds of observation you can see a hole in your hand. Can you see it? If you are not able to see it, try this trick with your other hand and other eye.
How it happens?
Your left eye and right eye see and send different visual information to your brain. Usually, the image information send by your both eyes will almost be the same. Therefore, your brain has no problem in combining the right and left images together. However, this trick forces your right and left eyes to see images that are so different. Then your brain blends them incorrectly. This will cause a creation of an image of a hole in your hand.